It is known to provide a valve assembly for controlling flow through a flow passage. For instance, in a prior art intake device for an internal combustion engine, a valve assembly is included with an intake air quantity control valve such as a throttle valve or the like. The valve opens and closes therein and is fitted to a downstream end side of an air duct. An outlet port side of the throttle body is coupled to an upstream end side of an intake manifold. Also, a first sealing member such as a first gasket is provided for sealing the space between the throttle valve and the air duct, and a second sealing member such as a second gasket is installed for sealing the space between the throttle body and the intake manifold. For example, Japanese Patent Publication No. 10-259768A discloses such a valve assembly.
However, in the case of the valve assembly disclosed in Japanese Patent Publication No. 10-259768A, the first gasket and the second gasket are separate sealing members. As such, the valve assembly is overly complicated and the manufacturing costs are relatively high.
For instance, the present applicant has filed Japanese Patent Application No. 2005-228675 (filed Aug. 8, 2005, hereinafter referred to as “comparative example 1”). This application discloses an intake manifold in an intake duct of an internal combustion engine. A flow of intake air inducted into each cylinder of the engine is switched corresponding to an operating condition of the engine to thereby improve a combustion condition and engine performance. The intake device for the engine of this comparative example 1, as shown in FIG. 8, comprises an intake duct that supplies inducted air (i.e., intake air) into a combustion chamber of the engine. The intake duct includes an intake manifold 102 that defines an intake passage 101, a head cover 104 that defines an intake passage 103, and a cylinder head 106 that defines an intake air port 105 and that communicates with a combustion chamber.
A valve unit 110 is also provided the intake manifold 102. The valve unit 110 includes a housing 111, which is disposed in a fitting hole 107 formed in the intake manifold 102. The valve unit 110 also includes an intake control valve 112, which rotates relative to the housing 111 to open and close an airflow path 109. Furthermore, the valve unit 110 includes a valve shaft 113 having a center of rotation at opposite sides of the intake control valve 112. The valve shaft 113 is formed integrally with the intake control valve 112 and is rotationally supported by respective side walls of the housing 111 via bearings (not shown). Airflow through the airflow path 109 is indicated in FIG. 8 by arrows.
A first gasket 131 is provided between a first annular recessed part 121 formed at the downstream end surface of the intake manifold 102 and the upstream end surface of a head cover 104. The first gasket 131 seals the gap formed between the intake manifold 102 and the head cover 104. Also, a plurality of second gaskets 132 is provided between the inner wall of the fitting hole 107 of the intake manifold 102 and the outer wall of the housing 111 of the valve unit 110. More specifically, the second gaskets 132 are provided in second annular recessed parts 122 formed at the outside wall surface of the housing 111 of the valve unit 110, are inserted two second gaskets 132. The second gaskets 132 seal the gap formed between the intake manifold 102 and the housing 111 of the valve unit 110.
Engine vibration is transmitted to the valve unit 110 via the head cover 104 and the intake manifold 102. There is a possibility that the valve unit 110 in the interior of the fitting hole 107 of the intake manifold 102 can vibrate in a direction transverse to the axis of the flow path 109 (i.e., in the Y-direction and/or Z-direction indicated in FIG. 8). Thus, to dampen this vibration, the two second gaskets 132 are arranged to encompass the housing 111 of the valve unit 110.
The valve unit 110 has a contact surface 114 that abuts against the control surface 141 (i.e., X-direction alignment surface) of the intake manifold 102 at the upstream side of the housing 111. Also, the position of the valve unit 110 in a direction transverse to the axis of the airflow path 109 is determined by sealing position of the second gaskets 132.
However, in the intake device for the engine of the comparative example 1, similar to the intake device disclosed in Japanese Patent Publication No. 10-259768A, the first and second gaskets 131, 132 are separate members. As such, the seal structure of the intake device is overly complicated, and the manufacturing costs are relatively high.
Moreover, a reaction force is applied from the intake manifold 102 through the second gaskets 132 to the housing 111, and the reaction force can deform the housing 111. As such, the gap between the housing 111 and the intake control valve 112 may be insufficient for ensuring proper rotation of the intake control valve 112.
Also, the engine head cover 104 is, for example, a cast metal article such as aluminum die-cast or the like, and has an upstream side end surface for attaching to the intake manifold 102. Typically, this upstream side end surface is precision cut to high tolerances. The intake manifold 102 is a resin molded article which is integrally resin molded.
Since the control surface 141 (i.e., X-direction alignment surface) of the intake manifold 102 is spaced relatively far away from the downstream side end surface 142 of the intake manifold 102, the assembly position of the valve member 110 in the direction of the axis of the airflow path 109 (i.e., the X-direction) is relatively imprecise. Accordingly, it may be difficult to align the pivotal center of the valve shaft 113 with through holes in the intake manifold 102. Therefore, after the valve unit 110 has been positioned inside the fitting hole 107 of the intake manifold 102, it may be difficult to insert a shaft 116 from outside the intake manifold 102 through the valve shaft 113 of the valve unit 110. Also, because of an axial deviation of the assembly position of the intake control valve 112 in relation to the intake passage 103 and/or the intake air port 105, engine combustion conditions and/or engine performance can be detrimentally affected.